The traditional process for paving roadways with asphalt paving material is generally carried out by an asphalt paving machine and a number of supply trucks which transport the asphalt paving material from an asphalt production plant to the paving machine. The paving machine generally is self-propelled and is driven by a wheeled or tracked drive system. A hopper is located at the front end of the machine to receive asphalt paving material from a dump-type supply truck, and a floating screed is located at the rear end of the machine to form the asphalt mat. A conveyor delivers the asphalt paving material from the hopper to a transversely oriented distributing auger just ahead of the screed that discharges the asphalt paving material across the roadway in front of the screed.
Sometimes, asphalt paving material is discharged directly from a delivery truck into the hopper of the asphalt paving machine. A typical asphalt paving machine has a hopper with a capacity of 5-15 tons, whereas a typical dump-type delivery truck has a capacity of about 20 tons. The front of the paving machine is usually provided with rollers which are adapted to engage the rear tires of a delivery truck. This arrangement enables asphalt paving material to be transferred from the truck to the asphalt paving machine by positioning the delivery truck in front of the paving machine and raising the dump bed of the truck to allow the asphalt paving material to slide down the bed into the hopper of the paving machine as the paving machine pushes the truck along in front of it. However, because the delivery truck usually carries more asphalt paving material than the hopper can receive at one time, it may be necessary for the paving machine to push the delivery truck along for several minutes while its conveyor transports the asphalt paving material out of the hopper to the distributing auger in front of the screed. This may be difficult to manage when the paving machine is proceeding through intersections or operating on curved sections of the roadway.
Furthermore, when the truck bed of the delivery truck is raised, it should not come into contact with the hopper of the paving machine, and it should not be carried by or ride on any portion of the paving machine. For smaller-capacity dump trucks, contact with the hopper of the asphalt paving machine is not often a problem. However, such contact can be a problem when large tractor-semitrailer units are used as delivery vehicles, particularly when the truck bed is extended to its highest point. In addition, if a delivery truck contacts the asphalt paving machine so that a portion of the weight of the delivery truck is carried by the paving machine as the paving operation is carried out, the screed elevation may be changed, which will affect the elevation of the finished asphalt mat.
When asphalt paving material is delivered directly to a paving machine by delivery trucks, it is frequently necessary for a series of delivery trucks to move into contact with the front end of the paving machine to serially discharge their loads into the paving machine's hopper. This method of delivery requires multiple truck maneuvers that are often difficult to carry out without stopping the paving machine. However, when a paving machine stops and subsequently restarts, its floating screed will produce a dip in the asphalt mat (when the machine stops) and a bump (when it restarts). Furthermore, the ability of the paving machine operator to place a smooth mat on the roadway will be affected by the rate of feed of asphalt paving material to the paving machine. This requires planning for proper scheduling of delivery trucks and coordination with the asphalt production facility. However, delays at the production facility or traffic encountered by the delivery trucks can thwart the efforts of the most careful planners. Consequently, because it is desirable to keep the paving machine moving at all times during an asphalt paving operation, and since delivery trucks must be unloaded as they are pushed along in the paving direction, it is frequently necessary to have delivery trucks queue up near the paving machine to ensure that a loaded truck is available to move quickly into unloading position as an unloaded truck is moved out of the way. This may result in heat losses in the asphalt paving material in the waiting trucks, which can affect the quality of the asphalt mat being created by the paving machine.
Because of the difficulties associated with the timely delivery of asphalt paving material by individual delivery trucks directly to a paving machine, material transfer vehicles have been used in recent years to transport asphalt paving material to asphalt paving machines engaged in paving operations. One type of material transfer vehicle may be used to shuttle asphalt paving material between the delivery trucks and an asphalt paving machine. Such a self-propelled material transfer vehicle typically includes a material-receiving device comprising a large-capacity truck-receiving hopper or a windrow pick-up head, and an inclined receiving conveyor extending upwardly from the material-receiving device. Asphalt paving material carried by the receiving conveyor from the truck-receiving hopper or windrow pick-up head is discharged off the elevated output end of the receiving conveyor into a chute mounted on the lower end of a discharge conveyor, or into an intermediate surge hopper that is sized to hold the entire load of a delivery truck. The discharge of asphalt paving material off the elevated output end of the receiving conveyor so that it may fall under the influence of gravity into a chute or surge hopper assists in preventing undesirable segregation of the various particulate components of the asphalt paving material by particle size.
Material transfer vehicles of the type that are equipped with a surge hopper typically include a surge hopper unloading conveyor in the surge hopper that is adapted to transfer the asphalt paving material to the discharge conveyor. Discharge conveyors mounted on material transfer vehicles with and without surge hoppers are generally pivotable about a substantially vertical axis so that the material transfer vehicle can be positioned alongside or in front of an asphalt paving machine that is laying an asphalt mat and rapidly discharge asphalt paving material into the hopper of the paving machine as the material transfer vehicle moves with the paving machine along the roadway. Because of its rapid loading and unloading capabilities, a self-propelled material transfer vehicle can rapidly shuttle between delivery trucks at a pick-up point and an asphalt paving machine that is laying an asphalt mat at a paving site so that there is less likelihood that the paving machine will have to stop paving because of a lack of asphalt paving material.
The receiving conveyor of a material transfer vehicle is typically a chain-driven drag conveyor. Such a conveyor starts and stops frequently during operation, and it carries a load that may be quite heavy at times. Consequently, it is necessary to adjust the tension of the drive chain on both sides of the conveyor from time to time. The chain tension is adjusted by manually using a wrench to adjust a bolt in a chain tension adjustment assembly that is located on opposite sides at the elevated output end of the receiving conveyor. Consequently, an operator of a material transfer vehicle having a surge hopper either has to climb into the surge hopper to gain access to the chain tension adjustment assembly, or he must use an external ladder or lift truck to gain the necessary access.
It would be desirable if a platform for access to the chain tension adjustment assembly of the receiving conveyor of a material transfer vehicle could be provided which is integrally incorporated into the housing structure of the material transfer vehicle. It would also be desirable if such a platform could also serve as a door for a recess in the structure of the material transfer vehicle that provides access to protected components (as hereinafter defined). It would also be desirable if a preferred embodiment of the platform could serve as a door for a recess in the structure of the material transfer vehicle that accommodates storage of the wrench or other tool that is used to adjust the chain tension.